Pumping apparatus



April 29, 1941. I w. F. MAYER 2,239,727

7 PUMPING" APPARATUS Filed March 21, 1938 9 Sheets-Sheet 1 April 1941-w. F. MAYER ruurme APPARATUS Filed RM 21. 1958 9 sheets-sheet 2 April29, 1941. w. F. MAYER PUMPING APPARATUS Filed March 21, 1938 9Sheets-Sheet 5 April 29, 1941. w. F. MAYER 2,239,727

PUMPING APPARATUS Filed larch 21, 195a 9 Sheets-Sheet 4 April 29, 1941.w. F. MAYER PUMPING APPARATUS Filed March 21, 1938 9 Sheets-Sheet 5 III, III

April 29, 1941. w MA-YER V 2,239,727

PUMPING APPARATUS Filed larch 21, 1938 9 Sheets-Sheet 6 April w; F.MAYER ruyrme APPARATUS Filedllarch 21, 1938 9 Sheets-Sheet '7 9Sheets-Sheet 8 MEN Bkkomm;4

April 29, 1941. w. F. MAYER PUMPING APPARATUS 9 Sheets-Sheet 9 FiledMarch 21, 1938 gwue/wto'b VIII; I

UNITED STATES PATENT OFFICE PUMPING APPARATUS Waldemar F. Mayan-LesAngeles, Calii., assi'gnor to Byron Jackson 00., Huntington Park, Calla,a corporation oi Delaware ApplicationMarch 21, 1938, Serial No. 197,14234 (01.103-52) This invention relates generally to hydrauli In one form,one cylinder constitutes a singlecylinder, double-acting hydraulic motorin which a motive liquid is admitted alternately to oppoinginterconnected for reciprocation in unison.

site ends to produce a power stroke of the piston in each direction. Theother cylinder constitutes a single-cylinder, double-acting pump inwhich the piston is direct-connected to the piston of the hydraulicmotor to be reciprocated thereby and .to pump liquid on each stroke. 7

In another form of this type of pump and the form illustrated herein,the hydraulic motor is interposed between the two halves of the pump,the inner side of each piston being subjected to motive liquid and theouterside of each piston being in contact with liquid to be pumped. Forreasons set-forth in detail in the copending application of AladarHollander, Serial No. 197,139, filed concurrently herewith, patentedJanuary 23, 1940, No. 2,187,972, the latter form of pump has manyadvantages over the first-mentioned form, particularly for handlingliquids at high pressure. However, the improvements constituting thepresent invention are intended to cure certain defects which arecharacteristic of both forms, and, while the improvements areillustrated and described as embodied in a pump of thesecond-mentionedform, it will be apparent that they are equally applicable to thefirstmentioned form or to any other form having similar operatingcharacteristics.

In this type of pump, liquid is pumped only from a single cylinder at atime, and, in the absence of any flow equalizing or compensating means,the discharge will be temporarily interrupted during reversal of thepiston at the end oi each stroke. While this may not be a seriousobjection under certain conditions, such as low pressure and rapidreversal, it constitutes a serious defect when attempting to pump athigh perative that the flow o1 motive liquid be continuous and thatpressure variations therein be reduced to a minimum. This is necessaryfor smooth performance or the pump, and is also highly desirable if thehydraulic pump is a part of a hydraulic system including other devicesoperated by motive liquid from v a common source. Pressure fluctuationsin the motive liquid resulting from irregular flow tothe pump wouldnaturally have a detrimental efiect on the operation of otherhydraulically operated devices of the system.

In adapting a hydraulic pump oi the aforementioned type to handlingliquids at high pressure, it has not only been discovered that it isessential to provide steady flow of the motive liquid and of thepumpdischarge, but also that uneven flow of suction liquid to the pumpand of spent motive liquid from the pump is highly objectionable. Whenoperating at low pressure and relative high velocity, the momentum oithe pumped liquid will continue the flow directly from the suction inletto the discharge outlet during stroke reversals; however, when operating.at high pressure this is not the case, and the suction and dischargeare interrupted completely at each reversal unless provision is made tocon-, tinue the flow. It is essential to smooth performance of the pumpat high pressure that the flow of all four liquids be steady.

In the copending application of Aladar Hollander and Waldemar F. Mayer,Serial No.

' 197,140 flied concurrently herewith, there is disclosed a .surgedevice operated by the motive liquid for providing continuous flow ofmotive liquid to the pump, of spent motive liquid from the pump, ofsuction liquid to the pump, and of discharge liquid from the pump, theoperation of the surge device being dependent on a slight pressure dropin the pump discharge.

A broad object of the present invention is to reduce to the greatestextent possible, liquid pressure and flow irregularities in a pistontype pump.

A more specific object is to provide a surge device for use with ahydraulically actuated piston pump, which device does not depend upon aninitial pressure drop to cause it to function, thereby making itpossibleto completely compensate for the pressure and flowirregularities normally resulting from piston reversal.

The foregoing objects are achieved in accordance with the presentinvention by employing a surge device operated in synchronism with thereversing valve of the pumps, by the motive liquid, but under thecontrol of an independent pressure fluid.

A feature of the invention is a hydraulic pump having a reversing valveactuated by a control pressure fluidindependent of the motive liquid,and a surge device operated by the motive liquid but controlled by thecontrol fluid in synchronism with the actuation of the reversing valve.

Other objects, features and advantages of this invention will beapparent from the following description of certain preferred embodimentsof the invention, taken in conjunction with the accompanying drawings,wherein:

Fig. 1 is a plan view of one form of pump constructed in accordance withthe invention;

Fig. 2 is a side elevation of the same pump;

Fig. 3 is an end elevation of the same pump;

Fig. lis a vertical longitudinal section through a portion of the pump,taken substantially in the line IV-IV of Fig. 1;

Fig.5 is a transverse vertical section taken approximately in the planeVV of Fig. 4;

Fig. 5 is a sectional view, taken approximately in the plane V V of Fig.5;

Fig. 59' is a sectional view, taken along the line V V of Fig. 5;

Fig. 6 is a transverse vertical section taken approximately in the planeVI-VI of Fig. 4.;

Fig. 601 is a horizontal section taken approximately in the plane VN-VIof Fig. 6;

Fig. 6h is a vertical section taken approximately in the plane V"I VI[of Fig. 6d;

Fig. 6k is a vertical section taken approximately in the plane VF -VI ofFig. 6d;

Fig. 7 is a fragmentary transverse vertical section taken approximatelyin the plane VHV11 of Fi 4;

Figs. 8 to 11, inclusive, are schematic diagrams illustrating theoperation of the pump;

Fig. 12 is a schematic diagram showing a modification of the structureillustrated in Figs. 1 to 11;

Fig. 12a is a schematic diagram similar to Fig.

12 but showing another modification;

Fig. 13 is a schematic diagram illustrating still another modificationand the invention; and

Fig. 14 is a schematic diagram illustrating a modification of the systemshown in Figs. 12 and 1211.

Referring to the form of the invention shown in Figs. 1 to 11, the pumpcomprises generally a central body A mounted on skids B and havingsecured thereto a pair of cylinders C, C in axial alinement on oppositesides of the central body. A valve housing D is secured to the uppersurface of the central body. An inlet pipe III for motive liquid underpressure is connected to one side of the valve housing, and a dischargepipe I I for spent motive liquid is connected to the opposite sidethereof. An inlet pipe I2 for a control fluid is connected to the top ofthe valve housing. A suction pipe l3 for liquid to be pumped isconnected to one side of the central body, and a discharge pipe l4 forpumped liquid is connected to the other side thereof. Inasmuch as thepump is particularly adapted to handle drilling mud used in drillingdeep wells, afld the motive liquid employed is usually water, the pumpedliquid will for convenience be termed mud and the motive liquid willbe-referred to as water.

The two cylinders C and C are identical, and hence a description of onewill suffice for both. Referring to Fig. 4, the cylinder C comprises anouter shell 2| closed at its outer end by an end plate 22 bolted to aflange 23 welded to the outer inlet pipe l3. As shown in Fig. 6, a mudsue-- end of the shell. A bolting flange 26 welded to the inner end ofthe shell is bolted to the side of the central body A. Supportedconcentrically within the shell 2! and coextensive therewith is acylinder 3i of slightly smaller diameter than the shell 2i, forming anannular channel 32 between the shell and cylinder. The outer end of thecylinder terminates short of the outer end of the shell, and issupported on an annular flange 33 integral with the end plate 22. Theflange is formed with a plurality of slots 3% spaced about the peripherythereof to provide communication between the interior of cylinder 3! andthe annular channel 32.

A central passage 33 and an outer concentric annular passage 39 areformed in each side of the central body A, forming an annular flange d0between the two passages. The cylinder Si is supported at at on theouter periphery of the flange W, and the outer shell 2% isbolted to thecentral body A concentrically with the annular passage 39. The interiorof cylinder Ill is thus in communication with the passage 33 and theannular channel 32 is in communication with the annular passage 39. Thepassages 35 and 39 communicate with other passages cored in the centralbody and leading to mud and water valves, as will be describedhereinafter.

Pistons 45 and 45' are reciprocable in the cylinders 3| and 3|respectively and are secured to the ends of a, piston rod 41 extendingthrough a bore 48 in the central body into each cylinder. A stuffing box49 seals the piston rod in fluidtight relation to the central body.

Formed Within the central body is a mud suction chamber 55 communicatingwith the mud ticn valve 56 controls communication between chamber 55 andthe annular passage 39 leading to the annular channel 32. A similar muddischarge valve 51 controls communication between passage 39 and adischarge chamber 58 leading to the mud discharge pipe I4, as shown inFig. 5. It will be understood that both halves of the pump on oppositesides of a central transverse plane, represented by line VV of Fig. 4,are identical, and that mud suction and discharge valves are alsoprovided between chambers 55 and 58 and the annular passagev 39 leadingto the right-hand annularpassage 32. Since all parts on one side of line5-5 are identical with those on the other side, those to the right ofthe central plane, as viewed in Fig. 4, will be designated by primedreference numerals corresponding to the unprimed numerals used todesignate corresponding parts on the left side.

As shown in Fig. 4, the pistons are at the extreme left ends of theircylinders. On movement of the pistons to the right, mud will be forcedout of the right-hand cylinder 3| ahead of piston 45', through slots 34'in the end plate 22' into the annular channel 32', thence throughpassage 39' to discharge chamber 56, the valve 51 being lifted by theexcess pressure below it. At the same time, suction mud will be drawn bythe left-hand piston into suction channel 55, past valve 56 into theleft-hand passage 39, thence through the annular channel 32 and slots 34into cylinder 3i.

In order to reciprocate the pistons 45 and 45' in their cylinders, waterunder pressure is admitted to the cylinders alternately, under controlof a reversing valve. As shown herein, the reversing valve isactuatedhydraulically, and is controlled by a pilot valve which ismechanical- 'ly operated at the end of each stroke of the main pistons.Inasmuch as the pilot valve operating mechanisms are identical, only onewill be described. Referring to Figs. 4 and '1, a sleeve 8| is securedto the piston rod 81 adjacent the inner side of each piston. A finger82' is fixed to the lower end of an operating shaft 88 so as to projectinto passage 38 in the path of the sleeve 8|. The shaft 83 is journaledin the central body and projects into the valve housing D for engagementwith an upper shaft section 84 journaled in the valve housing. Astufling box 85 prevents leakage of water from passage 38 around theshaft and into the valve housing. A lever 88 is keyed to the upper endof shaft section 88,

ver 86 or 88' is thus swung about the shaft axis and shifts the pilotvalve.

The pilot valve controls the admission of w ter under pressure to themain Valve. For reasons which will be explained hereinafter, thepressure of the water admitted to the pilot valve is relatively low. ascompared to that employed to reciprocate the main pistons, and will bereferred to iierein'after as control water. The control water inlet I2,(Fig. 4), leads to a central chamber 12 selectively connectible withports 13 and 13' by valves 18, 14'. Ports 13, 13 communicate withpassages 15, 15' leading to cylinders 18, 18' at opposite ends of themain reversing valve assembly. Ports 13, 13' may also be selectivelyconnected to exhaust chambers 11, 11' communicating with exhaust wateroutlet M (Fig. In the position shown in Fig. 4 the pilot valve has beenshifted to the left by the'engagement of sleeve 6| with finger 82', andcontrol water is admitted to passage leading to cylinder 18 at the leftend of the main valve. Port 13' is placed in communication with theexhaust chamber 11' to exhaust water from the right-hand cylinder 18' asthe main valve moves to the right.

A pair of shuttle pistons 8|, 8| are reciprocable in the cylinders 16,16', and are connected to opposite ends of a double, four-way valveconsisting of valves 82 and 82' connected by a stem 83. Each of thelatter valves selectively establishes communication between a centralpressure water chamber 84 and a port 85 or,

cylinder as will be described hereinafter. An additional pair of valves88, 88' control communication between ports 81, 81' and exhaust ports88, 88' communicating 'with exhaust ports 88,

88', as shown in Figs. 8 to 11.

In order to control the rate of movement of the main valve, andparticularly to check too rapid movement thereof, a dashpot arrangementis incorporated in each shuttle piston. Since the dashpots areidentical, only that at the left end, as viewed in Fig. 4, will bedescribed. The shuttle piston 8| and sleeve 88 are hollow to slidabiyreceive a stem 8| secured in stationary position in the valve housing.The stem is bored axially at 82 and is provided with a lateral port 83communicating with the bore 82. As the valve as sembly moves to theleft, the stem 8| moves into the hollow piston and sleeve. functioningas a plunger to force water outwardly through the bore 82 and lateralport 83. The rate of escape of water from port 88 is controlled by aneedle valve formed on the inner end of a valve stem 84 v threaded intothe bore 82. A handle 85 is provided for rotating the stem 84 and thusmoving the needle valve axially of the bore to vary the effective sizeof the lateral port 83.

As stated previously, surge means in the form of a double surge pistonand cylinder arrangement is provided to insure continuous flow, atsteady pressure, of pressure water, discharge water, discharge mud, andsuction mud. To accomplish this result, the movement of the surgepistons is correlated to that of the main pistons in such a way thatduring reversal of the stroke of the main pistons the combineddisplacement of main pistons and surge pistons is equal to thedisplacement of the main pistons during the stroke of the latter.

Referring to Fig. 5, a pair of alined surge cylinders MI and I82 aremounted in the central body A, and extend transversely of the maincylinders below the piston rod 41. Pistons I83 and I88 are reciprocablein the cylinders MI and I82, respectively, and are connected by a pistonrod I85 extending through a partition I88 and sealed thereto by astui'flng box I81. It will be seen from a comparison of Figs. 4 and 5that the surge cylinders and pistons are of the same diameter as themain cylinders and pistons, and that the piston rod I85 is of the samediameter as the piston rod 41. Consequently if the same relativepressures are exerted on opposite sides of the surge pistons as areapplied to the main pistons, the displacements will be equal.

The cylinder IN on the inner side of piston I83 is in communication witha vertically extending fluid passage III- connecting with the centralpressure water passage 88, whereby the inner side of piston I83 isconstantly exposed to the pressure of the power liquid employed toreciprocate the main pistons. The outer end of cylinder I8I is in opencommunication with the mud discharge chamber 88, thus constantlyexposing the outer side of piston I8l to discharge pressure. the waterpressure exceeds the mud pressure, it is apparent that the piston |8|would be moved to the extreme left and held in that position unless anoverbalancing pressure is applied to augment the mud discharge pressure.For this purpose, the relatively low pressure control water admittedthrough inlet pipe I2 is admitted to the right-handsurge cylinder I 82on the inner side of piston I84, to augment the discharge mud pressureexerted on the outer side of piston I83. The pressure of the controlwater may vary considerably, the essential requirement being that itexceed the difference between the power water pressure and the dischargemud pressure. If-the power water is supplied by a multi-stagecentrifugal pump, the control water may conveniently be bled from thefirst stage of the pump.

A fluid passage 2 extends parallel to the passage I I I, and isconnected at one end to the inner end of surge cylinder I82, and at theother end to Ports 81 and 81'. The outer end of cylinder I82 Since is inopen communication with the mud suction pipe is and suction chamber 55;v

The movement oi the surge pistons is correlated to that of the mainpistons by exerting the control water pressure against piston I N duringthe stroke oi the main pistons whereby the surge pistons are held at theright-hand end their cylwas inders, as viewed in Fig. 5, and by bleedingthe pistons approach the end of their stroke, thereby permitting thehigh water pressure exerted on piston I03 to movethe surge pistons tothe left, the movements oi the main and surge pistons during reversalsupplementing each other to produce a combined eiiect equal to that ofthe main pistons during their stroke. The admission of control water tocylinders I02 and its release therefrom is controlled by the shuttlevalves II, 88 and Bi, 88'. As shown schematically in Figs. 8 to 11, thefluid passage H2 of Fig. v is in open communication with ports 81 and"Zone of the latter being opened to the pilot valve when the main valveis at either end position, and both being closed while the main valve ismoving from crease in the discharge pressure while the ain pistons arereversing. High pressure water enterin cylinder II to the right ofpiston I03 prevents interruption of the flow of this fluid while themain valves 82," 82-are passing dead center. Also, while the main valvesare moving from one end position to the other, ports I1 and 81' areopened to communication with discharge orts 89 and 89', respectively.and the water fin-surge cylinder I02 to the left of piston I is bIed tothe exhaust pipe I2, the piston I be- "ing moved in unison with pistonII! by the rod 1 I05. The discharge of water from the pump is thuscontinued during reversal of the main pistons. Movement of piston I04tothe left also draws in mud through the suction pipe I3, so

that 'the'ficw of suction mud is continuous and steady.

An indicator rod H5 (Fig. 5) may be secured to the piston I03 to extendthrough a stufling box H6 in the closure plate III, whereby the movementof the surge pistons may be observed.

The mode of operation of the device will be understood from a study ofFigs. 8 to 11, wherein the pump is illustratedschematically' and theparts are shown in five diflerent positions during a cycle. In Fig. 8the pilot valve is shifted to the right, admitting control waterfrom-inlet I2 to the right-hand end of the main valve assembly throughport 13' and passage IS. The main valve is consequently at the extremeleft-hand position, establishing communication between high pressurewater inlet, I0 and the left-hand main cylinder 3| through passage 85,and causing the main pistons 45 and 45 to move tothe left. Mud is beingdisplaced i'rom cylinder 3| through discharge valve 51, and suction mudis being drawn into the rightshand cylinder 3| through suction valve55'. At the same time of piston 15' through it, discharge port 88', andwater outlet ii. In this position shuttle piston II is to'the left ofport 81', admitting control water to passage H2 and to surge cylinder Ito exert a counterbalanclng pressure on piston Ill. The high waterpressurev exerted against surge piston "3 from passage I l I is thusexceededby the combined discharge mud pressure in discharge chamberBlexerted against the outer face of piston m and the control pressureexerted against piston ill, and the surge pistons are held in theposition shown in Fig. 8.

Referring to Fig. 8a. the main pistons have almost reached the end oitheir. stroke, and the pilot valve has been tripped to its left-handpositionby the trip mechanism shown in Figs. 4 and '7. One immediateeiIect of the shifting of the pilot valve is to release the controlpressure from surge cylinder I02 through the pilot valve exhaust chamber11', allowing the high water pressure exerted against surge pistonIll.to start the letter moving outwardly. At the same time, controlwater is admitted through passage I5 to the left end of the main valveassembly, causing the latter to move to the right. Referring to Fig. 9,prior to the closing of port II by valve II, valve ll moves to the rightof port '8, establishing communication between the latter and port 81 toexhaust the control water from surge cylinder I02 as the surge pistonsmove upwardly. Further movement of the main valve assembly to the rightcauses-valve I to clear port 81', establishing communication between thelatter and exhaust port 89', providing additional fluid passage area forexhausting control water from cylinder been replaced by the displacementby the surge pistons. I

Further movement or the, main valve assembly to the position shown inFig. 11 results in establishing communication between high pressurewater inlet III and passage 85' leading to the right-hand cylinder II,and between the lefthand cylinder 3i and exhaust port 86 through passage85. The main pistons are thus moved to the right, causing displacementof mud from cylinder 3i through discharge valve 51' and drawingin of mudto cylinder 3| through suction valve 56. Valve 38 has closedcommunication between ports 81' and 39', and valve 8| has closedcommunication between ports I! and 89, thus cutting oi! escape ofcontrol water from cylinder I82- Valve 8i has opened port ll tocommunication with the pilot valve, admitting control water throughpassage ii! to cylinder I02, thus causing the surge pistons to retreatto their former position. when the main pistons appreach the oppositeends or their cylinders, the pilot valve will be tripped back to theright, and the above-described sequence will be repeated, except thatconditions on opposite sides of a central transverse plane will bereversed.

In Fig. 12 is illustrated schematically a slightly modified form of theinvention, the mode of operation of which is, however, substantially thewater is being displaced from cylinder 3i ahead same as that of thepreviously described form Inasmuch as the main cylinders and pistons andthe surge cylinder and pistons are substantially the same as inthe firstform, and in view of the fact that they are illustrated more or lessschematically, a brief description thereof will sumce. Main cylindersI3I and I3I are secured to opposite sides of a central body I32, and thecylinders have secured to their outer ends valve chambers I33, I33. Mudsuction valves I34 and I34 and mud discharge valves I35 and I35 aremounted in the valve chambers, and suction valves being disposed ininlet passages I35, I38 leading from a mud section header I31. A suctionpipe I38 supplies mud from, a suitable source. A mud discharge headerI39 connects the valve chambers on the discharge side of valves I35 andI35, and a mud discharge pipe I48 leads to the point of use. Mainpistons I45 and I45 areinterconnected by a piston rod I45 forsimultaneous reciprocation in cylinders BI and HI, respectively, thepiston rod I45 extending through a partition I41 in the central bodyI32- ,Sleeves I48, I48 are formed on the inner sides of the pistons, andare provided with tapered cam surfaces I49, I49 adapted to engagepiun'gers I58 and I58, respectively, as each piston approaches the innerlimit of its stroke. The plungers are reciprocable in transverselyextending bores II, I5I' formed in the central body I32, the outer endsof the plungers engaging belicrank levers I52, I52 pivotally mounted ona valve housing I53. A pilot valve generally indicated at I55 isreeiprocable in the valve housing, and comprises a pair of balancedvalves I51, I51 mounted on a valve stem I58. The ends of the valve stemare engaged by the bellcrank levers I52, I52, whereby the valves areshifted from one position to the other at the end of each stroke of themain pistons I48 and I48. Valve I51 controls communication between acentral water chamber I5I and a port I52, and between the latter and adischarge port I53. Valve I51 similarly controls communication betweencentral chamber I5I and a port I52, and between the latter and adischarge port I53.

A main reversing valve, generally indicated at I58, comprises a pair ofbalanced valves I51, I51,

. and a pair of shuttle pistons I58, I58 connected.

at opposite sides of the valves and reciprocable in cylinders I59, I59.Valve I51 controls communication between a central chamber HI and to aport I59 in the partition I81.

cylinder I83, a piston I84 in cylinder I82 and a piston I85 in cylinderI83, the pistons being connected by a piston rod I85 extending through apartition I81 separating the two cylinders. High pressure water isconstantly admitted to the inner end of cylinder I82 through a conduitI88 extending from the high pressure water inlet I11 The outer end ofcylinder I82 is in communication with the mud discharge through a pipeI98.

The outer end of low pressure surge cylinder I83 is in communicationwith the mud suction header I31 through a pipe I9 I. In order to apply acontrol pressure to the inner side of piston I85 to supplement thedischarge mud pressure on piston I84, as in'the previously describedform, a control pressure pipe I95 leads from a suitable source of waterat relatively low pressure to' a valve chamber I95. A port I91 in thechamber communicateswith the cylinder I 83 through a. port I98 in thepartition I81. A discharge port I95in the valve chamber is normallyclosed to communication with port I91 by a valve 288. The valveisnormally held against its seat by a compression spring 284 interposedbetween a piston 285 and a cap 288 threadedly connected to a cylinder281 in which the piston 285 is reciprocable.

In order to lift the valve 288 from its seat and release the controlpressure water from cylinder I83 during reversal of the stroke, of themain pistons, high pressure water is admitted to the cylinder 281beneath the piston 285 during the reversal of the main valve I55. Thisis accomplished by a control valve generally indicated at 2. Adouble-faced valve 2I2 is connected to the main valve I by a stem 2I3,whereby movea port I12 and between the latter and a discharge portI13, while valve- I51 similarly controls communication between thecentral chamber HI and Q a port I12 and between the latter and adischarge port I13. Ports I12 and I12 are contively, opening into themain cylinders I3I, I3I'.

Discharge ports I13, I13 communicate with a water discharge outlet I15leading back to the source of water. communicates directly withthe-central chamber I1I in the main valve and with the central chamberI5I in the pilot valve.

Ports I52, I52 in the pilotvalve communicate .nected to water passagesI15 and I15 respec-- ment of the main valve causes'the valve 2I2to shiftfrom one end of its housing 2I4 to the other end. Valve seats 2I5 and2I5 are formed at opposite ends of the valve. housing, whereby when thevalve is in its extreme right-hand position a high pressure water inletpipe 2" is closed, and

when the valve is at the opposite end of the housing the interiorthereof is sealed off from a The pepipe 2I8 leading to the cylinder 281.r'iphery of the central portion of the valve 2l2 is cut awayat intervalsto permit flow of presspring 284 is of suflicient strength to hold the Ahigh pressure water inlet I11 valve 288 on its seat against therelatively low be applied to the inner face of surge cylinder I85,

this pressure supplementing the discharge mud pressure on the outer faceof piston I84 to exceed the high water pressure on the inner face ofpiston I84. The surge pistons are thus held I in retracted positionduring the stroke of themain pistons.

The tripping of the pilot valve 'by one of thecamsI49 or I49 near theend of the stroke causes reversal of the main valve I55. During suchreversal the control valve 2I2 is moved from one end of its housing tothe other. The recesses 228 formed in the valve body permit flow of highpressure water from inlet I11 through conduits H88 and 211, through thevalve chamber 214 to conduit M8 and thence to the cylinder 201 beneathpiston 285. The valve 206 is thus lifted from its seat and the controlpressure water is released from cylinder I83 through discharge port !99which communicates with discharge post 116. The surge pistons are thuscaused to move in a direction to continue the flow of discharge mud,pressure water, suction mud, and exhaust water during reversal of themain valve.

As soon as the main valve reaches the end of its travel, the controlvalve 2!2 will be seated against seat 2l5 or MS, cutting of!communication between conduits 2 l1 and 2l3. The pressure of the watertrapped in conduit 2" and cylinder 261 is relieved through a smallbleeder opening 225 in the base of the cylinder 261,allowing the spring204 to return valve 206 to its-seat. The control pressure water enteringthrough conduit !95 is again forced into cylinder I83 and the surgepistons are returned to their original position.

Fig. 12a illustrates a modification of the arrangement shown in Fig. 12,whereby the separate control fluid is eliminated. This is accomplishedin Fig. 12a. by the provision of a valve-controlled bleeder by-pass fromthe high pressure side tothe low pressure side of the partitionseparating the surge cylinders.

the surge cylinders and pistonathespring-loaded release valve, and thecontrol valve connected to the main reversing valve are identical withthose of Fig. 12, and are designated by primed reference characterscorresponding to those designating corresponding parts in Fig. 12. Thestructure shown in Fig, 12a differs from that of Fig. 12, however, inthe manner of admitting control liquid to the low pressure surgecylinder I83 on the inner side of piston I85. In this instance a bleederpassage I35 extends through the central partition I31 to admit motiveliquid at a slow rate from the lower end of high pressure cylinder I82,the rate of flow through the bleeder passage being suitably controlledby a needle regulator valve 196'. This arrangement eliminates thenecessity of a separate control liquid such as is provided throughconduit I95 of Fig. 12.

In the operation of the form of the invention shown in Fig. 12a, duringthe normal stroke of the main pistons valve 208' is held on its seat byspring 204', preventing escape oifluid from the upper end of cylinderI83. High pressure motive liquid is constantly admitted to the lower endof cylinder 182' through conduit I88, and a small amount bleeds throughthe passage 165' in partition I81 into the upper end of cylinder I83,

to apply a force to piston I85 augmenting the force applied to pistonI84 by the discharge mud pressure sufficiently to retract the surgepistons and hold them in retracted position.

During reversal of the main valve, the control valve 2l2' (which isconnected to the main valve by stem 2!3' as in Fig. 12) admits highpressure motive liquid from line 2!1' to the cylinder 20'! beneath thepiston 285'. The valve 260' is thereby lifted from its seat, permittingthe escape of liquidirom the upper end of cylinder H3. The relief ofthis pressure permits the surge pistons to move upwardly, as viewed inFig, 120, to continue the flow of discharge mud, pressure water, suctionmud, and exhaust water during reversal of the main valve.

In Fig. 13 is illustrated schematically a still further modified form ofthe invention. The independent control of the surge pistons by theapplication and release, in synchronism with the actuation of thereversing valve, of a relatively low control pressure applied to thesurge pistons in opposition to the motive liquid pressure, is also afeature of this form of the invention. The valve arrangement forcontrolling the actuation of the main valve and for controlling theapplication and release of the control pressure is diiferent, however,from that shown in the two previously described forms.

The main cylinders 23! and 23! and their pistons 232 and 232' connectedby piston rod 233 are generally similar to'those previously described.Mud suction valves 234, 234 control. admission of mud to thecylindersfrom a suction header 235 having a mud inlet 236, while muddischarge valves 231, 231' control the discharge to a discharge header238 having a mud outlet 236.

Surge cylinders 245 and 246 contain surge pistons 241 and 246,respectively, connected by a piston rod 249. As in the two previouslydescribed 1 forms, the outer ends of the surge cylinders 248 and 246 areconnected, respectively, to the discharge header 238 and the suctionheader 235, while the inner ends of the cylinders 245 and 246 areconnected respectively to conduits 260 and 25!. Conduit 250 is connectedto the source of high pressure water, while conduit 25! is connected,through'valves to be later described, with the source of controlpressure water. As in the previously described forms, the applicationand release of the control pressure controls the movements of the surgepistons.

A balanced four-way mainvalve controls the admission of high pressurewater to the main cylinders, and comprises valves 26! and 26! connectedby stem 262. Shuttle pistons 263 and 263' are connected by rods 264,264' to opposite ends of the valves, and are reciprocable in shuttlecylinders 265, 265 by control pressure water admitted alternately toopposite ends to shift the valves 26!, 26! from one position to theother.

- In the position shown, high pressure water is adadmitted through aninlet 28!! communicating 1 with fluid passages 23! and 28! leading fromthe inlet to pilot valves 282, 282. It will be notedthat in this form ofthe invention separate pilotvalves are provided, only one being actuatedat the end of each stroke of the main pistons.

trol the actuation of the main reversing valve a branch passage 281leads to a port 288. When the valve is in the lower position shown, port268 is in communication with a port 289 lead Each pilot valve musttherefore coni ing to a port 283' controlled by the other pilot valve283'. When'the latter valve is inits lower position port 238'communicates with a port 289' leading to the surge cylinder 240 throughpassage 251. Hence it will be evident that when both pilotvalves are intheir lower positions, control water will be admitted to surge cylinder246 through inlet 230, passage 281, ports 233 and-289, ports 223' and233', and passageway when either pilot valve is raised by its respectivecam 284 or 234'- into the position in which valve 232' is shown, theadmission of control water to surge cylinder 235 is cut oil.

It will be apparent that themain valves 231 and 261 must be shifted tothe right, as shown, in order to admit high pressure water to theright-hand main cylinder. Consequently the right-hand pilot valve 282'must control admission of control water to the left-hand shuttlecylinder 265'to shift the main valve to the right. For this purpose a.port 295' is provided below the valve seat 236' of valve head 230',communicating with a p ssage 231' leading to shuttle cylinder 265. Whenpilot valve 232' is raised, the valve head 286' is lifted from its seatto admit control water to port 295', passage 291', and shuttle cylinder265. -At the same time the main valve and shuttle Pistons move to theright.

.The lifting of pilot valve 232' also establishes communication betweenport 203' and a dise charge port 233' communicating with a branchdischarge passage 233' leading to the main discharge passage 233, thusreleasing the control water from surge cylinder 245 and permitting thesurge pistons to move upwardly.

From the foregoing it will be seen that the lifting of pilot valve 282'admits control water to the left-hand shuttle cylinder tomove the mainvalve to the right, and that during the time the pilot valve is raisedcontrol water is cut oii from the surge cylinder 245. and the latter isexhausted to the exhaust passage. ment of the main pistons to the rightreleases the pilot valve, whereupon it moves to its lower position,reestablishing communication between ports 288' and 233' to admitcontrol water to surge cylinder 205 to returnthe surge pistons to theiroriginal position, thedischarge port 298' being out 01! fromcommunication with Move- 3 It will be apparent from the foregoingdescription of this form of the invention and its mode.

of operation that it embodies the same essential features of the threepreviously described forms, differing therefrom chiefly by the provisionof twoindependent pilot valves individually actuated by their respectivecam'sleeves, and each controlling the actuation of the main valve and Iof the surge pistons. The dashpots incorporated in the shuttle pistonsof Fig. 4, in the form first described,- may also be provided in thisform as well as in that shown in Fig. 12, whereby the rate of movementof the main reversing valve may be suitably regulated.

Fig. 14 illustrates a still further modification of a surge controlsystem applicable to a simplex nected at opposite ends to pistons 306.and 301.

The cylinders 302 and 303 are connected respectively at their outer endsto a mud discharge pipe 308 and a mud suction pipe 309 communicatingrespectively with the discharge and suction headers of the pump.

In this form of the invention, the opposite faces of the high pressuresurge piston 300 are exposed to motive liquid and dischargemud at equalpressures during the normal stroke of the main pistons. In this respectthis form distinguishes from each of the previously described forms,wherein the motive liquid pressurein the surge cylinder always exceedsthe discharge mud pressure. In the present instance. the pressure ofthese liquids is equalized during the normal stroke of the main pistons.and during the reversal period the full motive liquid pressure isadmitted to the lower end of cylinder 302 to actuate the surge pistons.

The motiveliquid and discharge mud pressures in cylinder 302 areequalized by means of a pressure regulator valve generally designated312. This valve comprises a'valve 313 connected to a valve stem 314 towhich is connected a piston 3 5 reciprocable in a cylinder 316. Thevalve 313 controls admission ofhigh pressure motive liquid from conduit311 to the lower end of surge cylinder 37-2. One face 313 of piston 315is exposed to the motive liquid in cylinder 302; wh le the other face319 of the pston is exposed to the discharge mud pressure through aconduit 320. By this arrangement the piston 315 and port 289' and be gopened to communication lifting of valve head 2" admits control waterfrom passage 281 topassage 235 leading to the right-hand shuttlecylinder 235', to shift the main valve to the left. At the same time,port 283 is closed, cutting 01! the control water from surge cylinder245, and communication is established between port 289 and exhaust port238 to discharge water from the surge cylinder 20! Ito the dischargeoutlet 2'13. Movement of the main pistons to the left, after reversal.of the main valve, releases the pilot valve 282 and allows it to returnto its lower position.

the .v-uve 313 connected thereto adjust themselves to establish apressure balance between the motive liquid and the d scharge mud. Inorder to avoid the possibility of valve 313 seating and being held onits seat by the motive liquid pressur a small amount of motive liquid isconstantly bled from cylinder 302 through a bleeder passage 322, thedischarge rate being suitably regulated by a manually adjustable needlevalve 323. The discharged liquid returns through a conduit 324 to thesource of motive liquid.

Duri"g the reversal of'the main valve of the pump. the regulator valve313 is opened wide to apply the full pressure of the motive liquid tothe piston 336. -To eifect the movement of valve 313 to full openposition, a second piston 32! is connected to the valve by a stem 321,and is reciprocable in a cylind 320 in axial align- 323 only duringreversal of the main reversing valve of the pump. A valve stem 33l isconnected to one end of the main reversing valve in a manner similar tothe connection of valve stem 2|3 to the main valve I66 of Fig. 12. Apair of valves 332 and 333 are connected to the stem 33[ to bereciprocated each time the main valve is reversed.

Inthe position shown in Fig. 14, the main valve is reversing and is inmid-position. and at this time the valves 332 and 333 are disposed onopposite sides ofa motive liquid inlet 334 and branch passages 335 and336 leading to the conduit 323. As the main valve approaches theright-hand end of its reversing stroke, the valve 332 closes the inletport 33|and simultaneously establishes communication between passage 335and an exhaust conduit 337, thereby relieving the piston 326 of thepressure of the motive liquid and permitting the valve 3" tore-establish equalized pressure on opposite sides of surge piston 336.Simultaneously, when the main valve moves from right to left, valve 332flr-st uncovers port 334 to admit motive liquid through passage 336 andconduit 323 to cylinder 323, and finally the valve 333 closes the inletport 333 and establishes com munication between passage 336 and anexhaust conduit 338.

The operation of this form of the invention is self evident from theforegoing description. It will be noted that the area of the inner faceof the piston 306 is less than that of the outer face by an amount equalto the cross-sectional area of the piston rod 305. Consequently, withequal unit pressures on opposite sides of the piston the total forceexerted by the mud will exceed that exerted by the motive liquid, andconsequently the piston will be retained in retracted position duringthis phase of operation. Also, it may be noted that the regulator valvedoes not'eflect exact equalization of pressures. because of the,

slightly reduced piston area 3" due to the piston rod 3| 4. However,because of the constant bleeding of motive liquid from the lower end ofcylinder 302 through the bleeder passage 322, the motive liquid pressurein cylinder 302 will be less thanthat in the cylinder MS of theregulator valve, and consequently the total force exerted on the piston336 by the mud pressure will eat-- ceed that exerted by the motiveliquid. This difference in opposing forces on opposite faces of piston336, together with the suction exerted on the outer face of piston 301by the negative pressure in the suction header of the pump, issufllcient to move the pistons to their retracted position during thestroke of the main pistons. During main valve reversal periods thepressure regulation is interrupted by admission of motive liquid tocylinder 328, causing the valve M3 to be opened wide to admit the motiveliquid at full pressure to the surge of cylinder 332.

It will be obvious that the surge control system of Fig. 14 coacts withthe main pistons of the pump in the same timed relation as in thepreviously described forms, the only difference residing in the mode ofretaining and releasing the surge pistons.

It will also be obvious that the control arrangements of Figs. 12 to 14may be embodied in a. pump constructed as in Figs. 1 to '7, inasmuch asall of the fluid pwsages communicate with the upper surface of thecentral body A to which the valve housing D is secured. Eachof theschematic valve arrangements of Figs. 12 to 14 is capable of beingembodied in a valve housing attachable to the central body A of Figs. 1to 7.

In each of the embodiments described, the pressure fluctuations normallyincidental to the reversal of the stroke of a simplex hydraulic pumphave been entirely eliminated, not only on Y the high pressure side butalso on the low pressure side. The control of the surge pistonsindependently of pressure variation is responsible for this eliminationof pressure fluctuations and makes possible a smoothness of operationunheard of heretofore in this type of pump. 37 suitable regulation ofthe control pressure and proper adjustment of [the dashpots controllingthe speed of travel or the main valve assembly, the length of thereversal period may-be suitably regulated in accordance with the pistonspeed of the main pistons.

A pump constructed in accordance with this invention is particularlyadapted to withstand the severe operating conditions imposed on mudpumps for handling drilling mud in connection with drilling deep wells.These conditions are set forth in the copending application of AladarHollander, serial No. 197,139, patented January 23, 1940, No. 2,187,972,referred to above, and will not be repeated here. It will be apparent,however, that the constructions described above embody all of thefeatures of the pump disclosed in the aforementioned application whichrender it admirably suited to this service, and, in

addition, the improved surge control is especially advantageous whenoperating at the high pressures required in deep well drilling. Irre-'spective of the pressure, the operation is smooth and characterized bythe absence of vibrations resulting from pressure fluctuations. whenoperated by pressure water supplied by a centrifugal pump, the balancedpiston arrangement results in the operating characteristics ofthe'centrlfugal pump being transmitted to the drilling mudunafl'ected'by any conflicting characteristics of the mud pump.Consequentlmwhen operating at relatively low pressure the mud volumewill be relatively high, while at high pressure the piston strokes willbe long, relatively slow, powerful strokes with correspondingly longerreversal periods during which the flow of all four liquids will becontinued unchanged. The result is a smooth, steady discharge of mud anda complete absence of vibration dueto waiter hammer in the drivingliquid. This latter feature is especially advantageous if the drivingfluid is also used to operate other hydraulic devices.

Having fully described the preferred embodiments of this invention, itis to be understood that I do not limit myself to the exact constructionherein set forth, which may obviously be varied in detail withoutdeparting from the spirit of this invention, but only as set forth inthe appended claims.

I claim:

1. In combination: a fluid-actuated pump responsive to motive fluidunder pressure for delivering a-pulsating flow of pump fluid, said pumphaving motive fluid inlet and outlet connections and pump fluid inletand outlet connections; piston means having a face communicating withsaid pump fluid outlet connection and movable in a'flrst direction toabsorb pump fluid from means for applying, only during intervals ofminimum flow of said pump, a force to said piston means opposing andexceeding the force normally'exerted by pump fluid thereon durmgintervals of maximum flow of said pump, to move the piston in saidopposite direction and supplement the pump discharge during saidintervals of minimum flow, said piston means moving in said onedirection under force of discharge fluid j to absorb discharge fluidfrom said pump during intervening intervals.

2. In combination: a fluid-actuated pump responsive to motive fluidunder pressure for delivering a pulsating flow of pump fluid, said pumphaving motive fluid inlet and outlet connections and pump fluid inletand outlet connections; piston means having a face communicating withsaid pump fluid outlet connection and movable in a first direction toabsorb pump fluid from said pump fluid outlet connection and movable inthe opposite direction to discharge pump fluid into said pump fluidoutletconnection, means for constantly urging said piston means in saidopposite direction with a force greater than the reactive rorce exertedon the piston means by the pump fluid to which it is exposed, and othermeans for applying, only during intervals of maximum flow of pump fluidfrom said pump, a force to said piston means supplementing the forceexerted by pump discharge fluid thereon, said other means being renderedinactive during intervals of minimum flow of pump fluid from said pump,whereby said piston means moves in said first direction to absorb aportion of the discharge of said pump during intervals of maximum flowand moves in said opposite direction to supplement the discharge of thepump during intervening intervals. v

3. A pump as described in claim 2, in which said means for urging saidpiston means in said opposite direction applies a force substantiallyproportional "to the pump discharge pressure.

4. Incombination: a fluidactuated pump responsive to motive fluid underpressure for delivering a pulsating flow of pumped fluid, said pumphaving motive fluid inlet and outlet connections and pump fluid inletand outlet connections; surge piston means having-a first, facecommunicating with said pump fluid outlet connection and movable in afirst direction to absorb pump fluid from said pump fluid outletconnection and movable in the opposite direction to discharge pump fluidinto said pump fluid outlet connection, said surge p ston means having asecond, opposing face communicating with said motive fluid inletconnection, said motive fluid. constantly applying a force to said surgepiston means greater than the opposing and reactive force exertedthereon by the pump discharge fluid to which it is exposed, and othermeans for applying, only during intervals of maximum flow of pump fluidfrom said pump, a force to said surge piston means supplementing theforce exerted by pump discharge fluid thereon, said other means beingrendered inactive during intervals of minimum flow of pumped fluid fromsaid pump, whereby said surge piston means moves in said first directionto absorb a portion of the dis- 5. Apparatus as described .in claim 4,in which said pump comprises main cylinder means and exposed to motivefluid bears thesame ratio to the area of the main piston face exposed topump liquid as the ratio of the area of said second opposing face ofsaid surge piston means to said first face of said surge piston means.

6. Apparatus as described in claim a, in which said surge piston meanshas an additional face oppositely directed from said first-mentioned.face and communicated with said pump fluid inlet connection" forequalizing flow of pump fluid through said inlet connection.

7. In ahydraulic pump, a pair of main cylinders, a main pistonreciprocable in each cylinder, said pistons being interconnected forreciprocation in unison, suction and discharge connections to said pump,inlet and exhaust connections for motive liquid for actuating said pump,a surge cylinder, a surge piston therein, said surge piston havingopposing faces exposed to thepressure of said pump discharge and of saidmotive liquid respectively, means to apply an auxiliary control ressureto saidsurge piston to supplement said discharge pressure, and means torelease said con= trol pressure during reversal of said main pistons.

8. In a hydraulic pump, a pair of main cylinders, a main pistonreciprocable in each cylinder, said pistons being interconnected forreciprocation in unison, suction and discharge connections to said pump,inlet and exhaust connections for motive liquid for actuating said pump,reversing valve mechanism for controlling the admission and exhaust ofmotive liquid, a surge cylinder, a surge piston therein, said surgepiston having opposing faces,- one exposed to the pressure of saidmotive liquid and the other exposed to the pressure of said pumpdischarge, means to apply an auxiliary control pressure to said surgepiston to supplement said discharge pressure, and means actuated at theend of each stroke of said main pistons for actuating said reversingvalve mechanism and for releasing said auxiliary control pressure.

9. A hydraulic pump comprising; a pair of main cylinders, a main pistonreciprocable in each cylinder, said pistons being interconnected forreciprocation in unison, suction and discharge connections to said pump,inlet and exhaust connections for motive liquid for actuating said pump,reversing valve mechanism for controlling the admission and exhaust ofmotive liquid, a pair of surge cylinders, a surge piston reciprocable ineach surge cylinder, said surge pistons being interconnected forreciprocation in unison, one of said surge pistonsbeing exposed on oneside to the motive liquid pressure and on the other side to thepump'disc'harge pressure, means charge of said pump during intervals, ofmaximum flow, and moves in said opposite direction tosupplement thedischarge of the pump during intervening intervals.

to apply an auxiliary control pressure to one-side of the other surgepiston to oppose the motive liquid pressure applied to the first surgepiston,

and means actuated at the end of each stroke of ed by a piston rodreducing the eflective areas of the face of said surge piston exposed tomotive liquid.

12. A pump as described in claim 8, in which said auxiliary controlpressure is released only duringreversal of said reversing valvemechanism. v 13. A pump as described in claim 8, in which saidlast-mentioned means includes a pilot valve, trip mechanism actuated bymovement of said main pistons for reversing said pilot valve, and anauxiliary valve mechanism connected to said reversing valve mechanismfor controlling the application and release of said control pressure tosaid surge piston.

14. A pump as described in claim 8, in which said last-mentioned meanscomprises a pilot valve actuated by movement of the main pistons withmeans responsive to movement of the pilot valve for actuating thereversing valve, and means including both the pilot valve and thereversing valve, for controlling application of said auxiliary controlpressure to said surge piston.

15. A hydraulic pump as defined in claim 8, in which said reversingvalve mechanism comprises a fluid-actuated main valve, and in which saidlast-named means includes a pilot valve, a control pressure fluid inletto said pilot valve, fluid connections from said pilot valve to saidmain valve whereby the latter is actuated by said control pressurefluid, and auxiliary valve mechanism connected to said main valve forcontrolling the admission to and release of control pressure fluid fromsaid surge piston insynchronism with the actuation of said main valve.

16. A hydraulic pump as defined in claim 8, in which said reversingvalve mechanism comprises a fluid-actuated reciprocating main valvecontrolling the admission and exhaust of motive liquid to said maincylinders, a shuttle piston connected to each end of said main valve andreciprocable in a shuttle cylinder, a. pilot valve, a

control pressure fluid inlet to said pilot valve,

fluid connections from said pilot valve to said shuttle cylinders, tripmechanism actuated by one of said mainv pistons at the end of eachstroke thereof for reversing said pilot valve to alternately admitcontrol pressure fluid to said shuttle cylinders to reverse said mainvalve, and fluid connections between said shuttle cylinders and saidsecond surge cylinder, said last-named connections being controlled bysaid shuttle pistons to control the application and release of controlpressure fluid to said surge piston,

1'7. A hydraulic pump as defined in claim 8, in which said reversingvalve mechanism comprises a fluid-actuated mainvalve, and in which saidlast-named means includes a pilot valve, a control-pressure fluid inletto said pilot valve, fluid connections from said pilot valve to saidmain valve whereby the latter is actuated by said conto said surgepiston when neither valve member is actuated, and to release saidauxiliary control pressure from said surge piston when either valvemember is actuated.

19. A pump as described in claim 8, in which said last-mentioned meanscomprises a pair of valve members successively actuated at opposed endsof the stroke of the main piston and connected to apply said auxiliarycontrol pressure to said surge piston when neither valve member isactuated, and to release said auxiliary control pressure from said surgepiston when either valve member is actuated, each of said valve members,when actuated, admitting auxiliary pressure fluid to said reversingvalve mechanism to reverse it. I

20. A pump as described in claim 8, in which said reversing valvemechanism comprises a fluid-actuated main valve, and in which saidlastmentioned means includes a pilot valve, an auxiliary controlpressure inlet to said pilot valve, fluid connections from said pilotvalve to said main valve, whereby the latter is actuated by saidauxiliary pump control pressure under con trol of said pilot valve, andauxiliary valve mech-- anism for controlling the admission to andrelease of auxiliary control pressure from said surge piston insynchronism with the actuation of said main valve, said auxiliary valvebeing controlled by said pilot valveindependently of said main valve.

21. A pump as described in claim 8, including a pair of independentlyoperable pilot valvesv adapted to be succmsively actuated at theopposi-te ends of the stroke of said main pistons, said' 'fluid underpressure, a third face on said surge piston means, means forcommunicating said control fluid inlet with said third face duringintervals of maximum flow of said pump, and releasing control fluid fromsaid third face during intervening intervals.

23. Apparatus as described in claim 4, in which said other meanscomprises an inlet for control fluid under pressure, a third face onsaid surge piston means, means for communicating said control fluidinlet with said third face during intervals of maximum flow of said pumpand communicating said third face on said surge piston means with saidmotive fluid outlet connection during intervening intervals.

24. Apparatus as described in claim 4, in which said other meanscomprises an inlet for control fluid under pressure, a third face onsaid surge piston means, means defining a restricted passage betweensaid control fluid inlet and said third face, and means for divertingcontrol fluid that has flowed through said restricted passage away fromsaid piston means, between intervals of normal flow of pumped fluid fromsaid pump.

25. In combination: a fluid-actuated pump comprising main cylinder meanshaving 'main piston means therein actuated by motive fluid underpressure for delivering a pulsating flow of pump fluid, said pump havingmotive fluid inlet and outlet connections and pump fluid inlet andoutlet connections, valve means for controlling the admission andexhaust of motive fluid to said pump; auxiliary cylinder means havingauxiliary piston means therein actuated by said motive fluid, saidauxiliary cylinder means having motive fluid and pump fluid inlet andoutlet connections which both said valve means are controlled bymovement 01 the main piston means.

28. The combination described in claim 25, in which both said valvemeans are fluid-actuated and controlled by a pilot valve actuatedresponsive to movement oi said main piston means.

29. In combination, a hydraulic pump having 20 piston means actuated by,motive liquid under pressure for delivering a pulsating flow of pumpliquid, said pump having motive liquid inlet and outlet connections andpump liquid inlet and outlet connections, valve means-for controlling thflow of motive liquid to said pump; auxiliary piston means actuated bysaid motive liquid for intermittently delivering pump liquid into thedischarge of said pump, auxiliary valve means for 30. The combination asdescribed in claim 29,

including auxiliary valve means controlling aotuation oi said auxiliaryP ton means, said auxiliary valve means being actuated in positivelytimed relation to said first-named valve means.

31. The combination as described in claim 29, including auxiliary valvemeans controlling actuation of said auxiliary piston means, saidauxiliary valve means being mechanically connected to said first-namedvalve means.

32. In a hydraulic pump, a pair of main cylinders, a main pistonreciprocable in each cylinder,

said pistons being interconnected for reciprocation in unison, suctionand discharge connections to said pump, inlet and exhaust connectionsfor motive liquid for actuating said pump, reversing valve mechanism forcontrolling the admission and exhaust or motive liquid, a surgecylinder, a surge piston-therein, said surge piston being operable todischarge pump liquid into said pump discharge connection in response topredetermined movement oi said surge piston, and means for eflectingsaid predetermined movement of said surge piston during and only duringmovement of said reversing valve.

33. In a hydraulic pump, a pair of main cyllnders, a main pistonreciprooable in each cylinder,

said pistons being interconnected for reciprocation in unison, suctionand discharge connections to said pump, inlet and exhaust connectionsfor motive liquid for actuating said pump, reversing valve mechanism forcontrolling the admission and exhaust of motive liquid, a surgecylinder, a surge piston therein, and means for eflectlng restoringmovement of said surge piston while and only while said reversing valveis stationary.

34. The combination as described in claim 2, in which said other meanscomprises another face on said piston means, and means for selectivelyapplying pressure fluid to said other face at a limited rate of flow.

WALDEMAR F. MAYER.

